1. Field of the Invention
The present invention relates generally to a system for providing individuals engaged in activity around a mobile working machine with an indication of the machine's location and, more particularly, to a warning system for alerting an individual who strays into a hazardous working zone of the machine during operation thereof.
2. Description of the Prior Art
Mobile working machines are used in many industrial and commercial applications to facilitate the performance of work-related tasks. Machines such as forklifts, front-end loaders, cranes, mining equipment and locomotives of all types have been used for many years to allow workers to perform tasks that otherwise would not be capable of being done. As these various types of working machines have evolved over time, it has been seen as an advantage in some instances to equip working machines with a remote control feature which removes the operator from the machine itself and thus allows the operator to not only control the machine but also perform other tasks when the services of the machine are not required. Equipping working machines with a remote control feature which allows the machine operator to also perform other tasks optimizes manpower and results in a cost saving for companies which employ this type of equipment. Remote control machines provide an added benefit in that they may be designed without considering the requirements necessary to protect an on-board operator and allow the operator to interface with the machine.
Although much effort has been spent in recent years attempting to provide remote controlled working machines of both the radio and hard-wired variety that may be operated safely at all times and in all working environments, it is well recognized that the use of these types of machines has led to the injury and, in some instances, death of mobile working machine operators and others working in close proximity to the machines. In recognition of the safety hazards these types of machines present, attempts have been made to design safety alarm systems capable of providing some form of audible or visual warning signal to machine operators and other personnel working around these machines that would indicate when a potentially dangerous working condition exists. However, the warning systems that have been proposed to date have not been sufficient.
For example, a doppler radar system has been investigated that is capable of providing an indicator to a mobile working machine operator that an obstacle is in the path of the machine. This radar system is intended to warn the machine operator that some object was in his path, but it has not been accepted from a safety standpoint since it only works with working machines that utilize an "on-board" operator and not with mobile machines that are remote controlled. In addition, the doppler radar system is incapable of distinguishing between an individual who had strayed too close to the machine and an inanimate object.
An ultrasonic sensing system has also been investigated as a mobile working machine alarm system. However, this system operates in a manner very similar to the doppler radar system in that it also cannot distinguish between an individual and an inanimate object. Infrared systems have been found unacceptable because they too cannot discriminate between individuals and objects and further they are subject to false alarms due to bright lights and reflections.
As seen from the foregoing, although various types of warning systems have been suggested for use with mobile working machines that are capable of providing a safety proximity alarm, all have shortcomings which preclude their use. Consequently, there is a need for an improved warning system operable to warn an individual of a potentially dangerous condition if he strays into the hazardous working zone of the machine.